When I was on chemo, the drugs would keep me awake for 3 days at a time. I lost the ability to make sense of numbers, alarming for me as a mathematician who can remember tons of numbers because each is like the face of an old friend. I sometimes lost the ability to make sense of time, I could not remember if something happened a day before, a week before, or months, and I could not sequence past events. steve made a short video about that strange experience.
After treatment, I slept terribly for a year and my thinking and memory were always foggy. Lack of sleep make a huge impact on my intelligence during that period (however I was extremely production and creative during that time as well. Weird.) I had resigned myself to my condition as my new normal, but my new new normal came around to be my old normal.